Detection of Nine M8.0-L0.5 Binaries: The Very Low Mass Binary Population and its Implications for Brown Dwarf and VLM Star Formation

Details Detection of Nine M8.0-L0.5 Binaries: The Very Low Mass Binary Population and its Implications for Brown Dwarf and VLM Star Formation Detection of Nine M8.0-L0.5 Binaries: The Very Low Mass Binary Population and its Implications for Brown Dwarf and VLM Star Formation

2003-01-06

arxiv.org/abs/astro-ph/0301095v1

Astrophys.J. 587 (2003) 407-422

Astronomy and Astrophysics

Astrophysics

To appear in the April 10, 2003 issue of The Astrophysical Journal 30 pages, 17 figures

Scientific paper

10.1086/368177

Use of the highly sensitive Hokupa'a/Gemini curvature wavefront sensor has allowed direct adaptive optics (AO) guiding on very low mass (VLM) stars with SpT=M8.0-L0.5. A survey of 39 such objects detected 9 VLM binaries. Most of these systems are tight (separation <5 AU) and have similar masses (Delta Ks<0.8 mag; 0.852.6 AU. This is slightly less than the 32+/-9% measured for more massive M0-M4 dwarfs over the same separation range (Fischer & Marcy 1992). It appears M8.0-L0.5 binaries (as well as L and T dwarf binaries) have a much smaller semi-major axis distribution peak (~4 AU) than early M binaries. We also find no VLM binary systems (defined here as systems with M_tot<0.185 solar masses) with separations >15 AU. We briefly explore possible reasons why VLM binaries are slightly less common, nearly equal mass, and much more tightly bound compared to more massive binaries. We find that a kick during the ejection of a forming VLM binary from a close triple or quadruple encounter (imparting a differential kick of ~3 km/s between the members of the binary) could reproduce the observed cut-off in the semi-major axis distribution at ~20 AU. However, the estimated binarity (~<5%; Bate et al. 2002) produced by such "ejection scenarios" is below the 9-15% observed. Similarly, the dynamical decay models of Sterzik & Durisen (1998); Durisen, Sterzik, & Pickett (2001) also cannot produce a VLM binary fraction above ~5%. Our estimate of a fragmentation-produced VLM binary semi-major axis distribution contains a significant fraction of ``wide'' VLM binaries with a>20 AU in contrast to observation. Hence more detailed theoretical work will be needed to explain this very interesting VLM binary population.

Affiliated with

Also associated with

No associations

Rating

Detection of Nine M8.0-L0.5 Binaries: The Very Low Mass Binary Population and its Implications for Brown Dwarf and VLM Star Formation does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

If you have personal experience with Detection of Nine M8.0-L0.5 Binaries: The Very Low Mass Binary Population and its Implications for Brown Dwarf and VLM Star Formation, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Detection of Nine M8.0-L0.5 Binaries: The Very Low Mass Binary Population and its Implications for Brown Dwarf and VLM Star Formation will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-722318